Touch panels are input devices installed on image display devices in which at least a portion thereof that overlaps with the image display device is transparent.
A known example of a touch panel is a resistive film type touch panel. In a resistive film type touch panel, a stationary electrode sheet and a movable electrode sheet, in which a transparent conductive coating film is formed on one side of a transparent base, are arranged so that the transparent conductive coating film are mutually opposed. An indium-doped tin oxide film (to be referred to as an ITO film) has widely been used for the transparent conductive coating film of these electrode sheets.
A sheet in which an ITO film is formed on one side of a transparent base (to be referred to as a ITO film forming sheet) has low flexibility and is easily immobilized, thereby making it preferable for use as a stationary electrode sheet of an image display device. However, in the case of using as a movable electrode sheet on the side of an input operator of a touch panel, it had the problem of low durability during repeated deflection.
Therefore, a flexible sheet in which is formed a transparent conductive coating film containing π-conjugated conductive polymer (to be referred to as a conductive polymer film forming sheet) is used on one side of a transparent base as a movable electrode sheet on the side of an input operator of a touch panel.
As a conductive polymer film forming sheet, Patent Document 1, for example, discloses a conductive polymer film forming sheet having a transparent conductive coating film formed from a composition containing a π-conjugated conductive polymer and a water-soluble epoxy on a transparent base.
However, the composition disclosed in Patent Document 1 has problems such that the composition is low in preservation stability and a coating film obtained from the composition is low in water resistance.